1. Field of the Invention
This invention relates to the bending of elongated workpieces, usually of a metallic, tubular nature and normally having a polygonal cross-sectional configuration, typically square or rectangular, by the action of forces applied thereto between a die and a pair of spaced anvils.
We are familiar with apparatus for curving or bending rods, pipe, tubing, straps or wire using a rigidly-supported cylinder whose piston rod has a pair of spaced rollers for imparting a thrust against a rigidly-supported rod to be bent. A third, rigidly-supported roller engages the rod at the concave surface of the bend in the rod. Oftentimes the rollers are called primary and secondary "dies" and in some instances the two secondary dies are adjustable toward and away from each other for the purpose of predetermining the desired bend configuration. It has also been suggested that the third or primary die be in the nature of a hemicylindrical member rather than a roller, as such, with all three dies power actuated during the bending operation as the primary die is shifted relative to the secondary dies.
In other instances the secondary dies are referred to as rotatable "posts" and the primary die is an adjustable "mandrel" actuated by the piston rod of a swingable cylinder with the tube bending around the mandrel. It has also been suggested that there be provided a "kinker" or crimper on the mandrel for purposely distorting the walls of square or rectangular tubing along the zone of bending, the theory being uniform distribution of excess material and preventing wall distortions. In such instances, opposed walls of the tubing bend inwardly toward each other at the bend. It is also not uncommon to use conical or cylindrical, detachable or replaceable rollers, with the distances therebetween being adjustable.
2. Summary of the Invention
In accordance with the concepts of our present invention, a pair of anvil plates are swingably mounted on a pair of long, stout wings each of which is, in turn, independently swingable and held in preselected positions in accordance with the needs of the operator or our tube bender.
The bender is also especially characterized by a die assembly of high utility in that a stack of die units is employed such that a multiplicity of differing, multi-plane bends can be made quickly and easily in a single workpiece without need for die changes or a number of separate benders. We contemplate also an open, unobstructed construction which permits top loading and unloading of the workpiece devoid of the need to "thread" the tube longitudinally thereof into and out of position between the dies and the anvils.
Another important feature of the instant tube bender relates to the way the stack of dies can be raised and lowered such as to properly align the selected die unit with the anvils and bring the same into proper relationship to a pair of tube-supporting rails.
Moreover, we provide for mechanism which releasably clamps all of the plates of the die assembly together, certain of such plates also gripping, in a vise-like manner, the tube itself to avoid improper distortion of the tube material while bending takes place.